When paints are applied manually or automatically to articles, some of the stream of paint, which in general contains both solids and solvents and/or binders, is not applied to the article. This portion of the stream is called overspray in the art. The overspray is absorbed by the air stream in the spray booth and supplied to a separation process.
In particular in the case of plant having a relatively high paint consumption, for example plant for painting vehicle bodies, it is preferable to use wet separation systems, in which methods of the type mentioned at the outset are used. In plant known from the market, water or oil is used as the separating liquid, and is mixed intensively and turbulently with the exhaust air from the booth and the overspray therein.
So that the particles of paint taken up by the separating liquid can be guided away from the separating surface without problems, the separating liquid must meet particular criteria. These include for example the fact that the adhesive action of the particles of paint must be overridden so that if they come into contact with the separating surface through the separating liquid they do not adhere thereto.
Moreover, the vapour pressure of the separating liquid must be kept at least low enough for the entrainment of gaseous components of the separating liquid by the exhaust air from the booth that flows past to be minimised as far as possible.
So that it is ensured that the separating surface is wetted as evenly as possible without sags or runs, the surface tension of the separating liquid must be sufficiently low.
In particular, it is desirable for the separating liquid to be able to flow down the separating surface in a largely laminar flow, that is to say that a thin film which moves down evenly is formed on the separating surface.
The present invention is directed to resolving these and other matters.